Mapeamento dinâmico de super-redes de Moiré em bicamada de grafeno rotacionada sob condicionamento térmico

Abstract

Emergent quantum phenomena, such as unconventional superconductivity, Mott insulators, and localized phonons, emerge when two graphene layers are stacked with a twist angle close to θ ≈ 1◦, known as the magic angle. Small deviations from this angle lead to deep changes in the electronic and structural properties of the system, known as magic-angle twisted bilayer graphene (MATBG). Thus, understanding the angular distribution and its stability under external pertubations becomes essential for advancing applications in nanoelectronics and quantum computing. In this work, we investigate the thermal dynamics and structural robustness of MATBG through confocal Raman spectroscopy and spatially resolved spectral analysis. By adapting and applying an angular analysis method to large-area spectral mappings, it was possible to identify moiré regions with different local twist angles. Three distinct structural regimes were identified: super-magic, magic, and non-magic regions. The super-magic regions, associated with previously unreported spectral contributions, disappear after annealing at 200 ◦C, while the magic and non-magic regions largely preserve their structural integrity even after successive annealing cycles up to 500 ◦C. We also observed that, following the thermal cycles, the local twist angles converged to values between 0.6◦ and 0.8◦ — an intermediate range in which the contribution of soliton-like structures becomes more pronounced. This behavior indicates the formation of a stable domain network, whose boundaries are governed by angular relaxation mechanisms mediated by solitons. These results reveal remarkable resilience of the vibrational properties, and by extension, of the electronic correlations in regions close to the conventional magic angle. Additionally, this work includes the development of a portable cryostat, featuring electronic thermal control and compatibility with Raman microscopy, enabling in situ thermal experiments on two-dimensional systems. Altogether, this study not only unveils the angular and phononic dynamics of MATBG but also offers a high-functionality instrumental tool for thermal studies in two-dimensional materials, establishing and elucidating paradigms in the engineering of correlated states in moiré structures.